On the optically-thick winds of Wolf-Rayet stars

Abstract

(abridged) The strong winds of Wolf-Rayet (WR) stars are important for the mechanical and chemical feedback of the most massive stars and determine whether they end their lives as neutron stars or black holes. In this work we investigate theoretically the mass-loss properties of H-free WR stars of the nitrogen sequence (WN stars). We connect stellar structure models for He stars with wind models for optically-thick winds and assess how both types of models can simultaneously fulfill their respective sonic-point conditions. Fixing the outer wind law and terminal wind velocity, we obtain unique solutions for the mass-loss rates of optically-thick, radiatively-driven winds of WR stars in the phase of core He-burning. The resulting mass-loss relations as a function of stellar parameters, agree well with previous empirical relations. Furthermore, we encounter stellar mass limits below which no continuous solutions exist. While these mass limits agree with observations of WR stars in the Galaxy, they are in conflict with observations in the LMC. While our results confirm in particular the slope of oft-used empirical mass-loss relations, they imply that only part of the observed WN population can be understood in the framework of the standard assumptions of a smooth transonic flow and compact stellar core. This means that alternative approaches, such as a clumped and inflated wind structure, or deviations from the diffusion limit at the sonic point may have to be invoked. Qualitatively, the existence of mass limits for the formation of WR-type winds may be relevant for the non-detection of low-mass WR stars in binary systems, which are believed to be progenitors of Type Ib/c supernovae. The sonic-point conditions derived in this work may provide a possibility to include optically-thick winds in stellar evolution models in a more physically motivated form than in current models.

arXiv commentaccepted by Astronomy & Astrophysics

References in corpus (25)

• On the metallicity dependence of Wolf-Rayet winds
• The Galactic WN stars: Spectral analyses with line-blanketed model atmospheres versus stellar evolution models with and without rotation
• Mass loss from late-type WN stars and its Z-dependence: very massive stars approaching the Eddington limit
• A Porosity-Length Formalism for Photon-Tiring-Limited Mass Loss from Stars Above the Eddington Limit
• The Galactic WC stars: Stellar parameters from spectral analyses indicate a new evolutionary sequence
• The Wolf-Rayet stars in the Large Magellanic Cloud: A comprehensive analysis of the WN class
• Neglecting the porosity of hot-star winds can lead to underestimating mass-loss rates
• Wind modelling of very massive stars up to 300 solar masses
• Stellar and Wind Properties of LMC WC4 stars - A metallicity dependence for Wolf-Rayet mass-loss rates
• Stellar envelope inflation near the Eddington limit. Implications for the radii of Wolf-Rayet stars and luminous blue variables
• The Eddington factor as the key to understand the winds of the most massive stars. Evidence for a Gamma-dependence of Wolf-Rayet type mass loss
• Massive main sequence stars evolving at the Eddington limit
• Local Radiation Hydrodynamic Simulations of Massive Star Envelopes at the Iron Opacity Peak
• Hydrodynamic model atmospheres for WR stars: Self-consistent modeling of a WC star wind
• Predictions of variable mass loss for Luminous Blue Variables
• Towards a better understanding of the evolution of Wolf-Rayet stars and Type Ib/Ic supernova progenitors
• Core-halo Structure of Chemically Homogeneous Massive Star and Bending of Zero-Age Main-Sequence
• The transition mass-loss rate: Calibrating the role of line-driven winds in massive star evolution
• Predicting the Presence of Companions for Stripped-Envelope Supernovae: The Case of the Broad-Lined Type Ic SN 2002ap
• Two bi-stability jumps in theoretical wind models for massive stars and the implications for Luminous Blue Variable supernovae
• Mass loss from inhomogeneous hot star winds III. An effective-opacity formalism for line radiative transfer in accelerating, clumped two-component media, and first results on theory and diagnostics
• Stellar mass-loss near the Eddington limit. Tracing the sub-photospheric layers of classical Wolf-Rayet stars
• An explanation for the curious mass loss history of massive stars: from OB stars, through Luminous Blue Variables to Wolf-Rayet stars
• Diagnostic of the unstable envelopes of Wolf-Rayet stars
• On the Launching and Structure of Radiatively Driven Winds in Wolf-Rayet Stars

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• Theory and Diagnostics of Hot Star Mass Loss
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• The temperature dependency of Wolf-Rayet-type mass loss: An exploratory study for winds launched by the hot iron bump
• Very Massive Stars and Pair-Instability Supernovae: Mass-loss Framework for low Metallicity
• Evolution of Wolf-Rayet stars as black hole progenitors
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• Nebular emission from young stellar populations including binary stars
• A synthetic population of Wolf-Rayet stars in the LMC based on detailed single and binary star evolution models
• Physics and evolution of the most massive stars in 30 Dor. Mass loss, envelope inflation, and a variable upper stellar mass limit
• Wind nebulae and supernova remnants of very massive stars
• Dynamically inflated wind models of classical Wolf-Rayet stars
• Stripped-Envelope Stars in Different Metallicity Environments I. Evolutionary Phases, Classification and Populations
• Red noise and pulsations in evolved massive stars
• CG X-1: an eclipsing Wolf-Rayet ULX in the Circinus galaxy
• Type Ia supernovae from non-accreting progenitors
• Populations of evolved massive binary stars in the Small Magellanic Cloud I: Predictions from detailed evolution models
• Spectroscopic and evolutionary analyses of the binary system AzV 14 outline paths toward the WR stage at low metallicity
• Thermonuclear and Electron-Capture Supernovae from Stripped-Envelope Stars
• The Wolf-Rayet Stellar Response To The Iron Opacity Bump: Envelope Inflation, Winds, and Microturbulence
• Helium-Star Models with Optically Thick Winds: Implications for the Internal Structures and Mass-Loss Rates of Wolf-Rayet Stars
• Wolf-Rayet -- compact object binaries as progenitors of binary compact objects
• Evolution of stars with 60 and 200 Msun: predictions for WNh stars in the Milky Way
• From Common Envelope Evolution to Luminous Red Novae I: A One-dimensional Radiation Hydrodynamic Model
• Dynamically consistent analysis of Galactic WN4b stars
• Polarization of light from fast rotating Wolf-Rayet stars: A Monte Carlo simulations compared to analytical formula